[doc] Make Hugo server not watch for changes to fix local previews.
[doc] Make Hugo server not watch for changes to fix local previews.

New symlinks introduced by the Bazel migration were causing Hugo to hang
on local previews because (it looks like) the procedure that watches
files for changes doesn't ignore symlinks listed in the configuration's
`ignoreFiles`. This passes `--watch=false` to Hugo server to avoid that
issue (at the unfortunate cost of local previews no longer automatically
updating).

Signed-off-by: Jade Philipoom <23b156e860ef6ab36b055884a79031aa7723874a@google.com>

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